The present invention relates to improvements in an air-conditioning control box mounted on an automotive instrument panel.
A generally-applied air-conditioning control box of this kind is shown in FIG. 5, where the box is generally indicated by numeral 1. The control box 1 comprises a casing 3, a light source 15, and a light transmission member 21. Note that FIG. 5 is a partial cross section of the control box 1. The design provided on the front surface 3 of the control box 1 is shown in FIG. 4.
The casing 3 is provided with a certain number of holes 7 for receiving air-conditioning control means, or knobs 5. A cylindrical retainer 9 for retaining the light transmission member 21 extends from the underside of the fringe of each hole 7. A light source retaining portion 11 is formed at the lower end of the retainer 9. The surface of the retaining portion 11 which faces the light source 15 is made white or otherwise treated so as to act as a reflective surface 13.
The light source 15 comprises a light bulb 17 and a socket 18. This socket 18 is rigidly fixed to the lower wall of the light source retaining portion 11. An electrical cord 19 for the light source 15 is connected to a battery (not shown).
The light transmission member 21 is a cylindrical member made from a transparent resin, such as acrylic resin. The light transmission member 21 is undercut and held to the retainer 9 of the casing 3. The air conditioning control means 5 is slid and fitted in the light transmission member 21. Almost the whole transmission member 21 is covered with the retainer 9, but it has an extension 27 disposed facing the light source. The outer surface of the extension 27 forms a light-incident surface 23. Light directly coming from the light source 15 and light reflected from the reflective surface 13 enters the transmission member 21 through the light-incident surface 23 and are transmitted in the transparent transmission member 21 while reflected diffusedly. Finally, the light is substantially uniformly emitted from the upper end surface of the transmission member 21. That is, the upper end surface forms a light-emitting surface 25. Structures similar to that shown in FIG. 5 are provided for the respective holes 7.
In the air-conditioning control box 1 constructed as described above, the light from the light source 15 makes bright the light-emitting surface 25 disposed around the air-conditioning control means 5. Therefore, the control means 5 seems to be afloat.
In the above-described air-conditioning control box 1, however, one light source 15 is required for each light transmission member 21. Hence, the number of the components is large, increasing the cost of the product.
Furthermore, in order to make the brightness of the light-emitting surface 25 uniform, it is necessary that light be reflected sufficiently diffusedly inside the transmission member 21. Therefore, if the distance between the light-emitting surface 25 and the light-incident surface 23 is short, the brightness of the light-emitting surface 25 may not be made uniform. Accordingly, the transmission member 21 is made large in size. This makes it impossible to realize the demand for miniaturization of the casing 3.